2,2',2"-Nitrilo[triethyl-tris-(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2 '-diyl) phosphite] is a compound having the formula I ##STR1##
This compound of formula I is useful as a processing stabilizer for organic polymers as taught in U.S. Pat. Nos. 4,318,845 and 4,374,219. The compound of formula I is disclosed as being a white powder melting at 121.degree.-134.degree. C. As such, the powdery product has defects in terms of handling and apparent density, exhibiting poor flowability, meterability, storage stability and hydrolytic stability.
It has now been found that the compound of formula I can be obtained in a different crystalline modification as purified crystalline particles which exhibit acceptable properties in respect to handling, apparent density, flowability, meterability, storage stability and hydrolytic stability.
The new modification is characterized by a triclinic crystalline form, melting in the range of 200.degree.-207.degree. C. as given by the peak temperature of the endotherm recorded by differential scanning calorimetry (DSC); and by an X-ray diffraction pattern obtained using Cu-K.alpha. which exhibits diffraction angles (2.THETA.) of very high intensity at 8.4 and 17; lines of high intensity at 9.9, 10.6, 11.4, 17.5, 19.1, 20.2; lines of medium intensity at 4.6, 4.9, 7.1, 12.7, 13.2, 13.6, 15.3, 15.8, 16.4, 16.7, 18.4, 19.7, 21.7, 23.4; and lines of weak intensity at 7.8, 8.8, 9.4, 12, 14.1, 14.6, 21, 22.3, 22.8, 23.9, 24.7, 25.3, 25.5, 26.4, 27.27.7, 28.4 and a relative absolute configuration of the three stereo axes of the dibenzo[d,f][1,3,2]dioxaphosphepin rings of R*,R*,S*.
R* and S* follow the customary convention when the absolute configuration of a molecule is unknown. The nomenclature adopted here is based on recent Chemical Abstracts Service practice as described by L. C. Cross and W. Kylne, Pure Appl. Chem. 45, 11-30 (1976).
The instant invention also relates to processes for the preparation of this novel beta crystalline modification of the compound of formula I.
The instant invention also pertains to a composition stabilized against thermal, oxidative and actinic induced degradation which comprises
(a) a polyolefin, and
(b) an effective amount of the beta crystalline form of 2,2',2"-nitrilo[triethyl-tris-(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2, 2'-diyl)phosphite], characterized by melting in the range of 200.degree.-207.degree. C. and by an X-ray diffraction pattern exhibiting lines of very high intensity at 8.4 and 17; lines of high intensity at 9.9, 10.6, 11.4, 17.5, 19.1, 20.2; lines of medium intensity at 4.6, 4.9, 7.1, 12.7, 13.2, 13.6, 15.3, 15.8, 16.4, 16.7, 18.4, 19.7, 21.7, 23.4; and lines of weak intensity at 7.8, 8.8, 9.4, 12, 14.1, 14.6, 21, 22.3, 22.8, 23.9, 24.7, 25.3, 25.5, 26.4, 27.27.7 , 28.4 and a relative absolute configuration of the stereo axes of the dibenzo[d,f][1,3,2]dioxaphosphepin rings of R*,R*,S*.
Preferably, the polyolefin is polypropylene.
One process for the preparation of the instant beta crystalline modification comprises heating a melt of the compound of formula I at a temperature in the range of 170.degree. to 200.degree. C. until the novel beta crystalline modification forms or optionally seed the melt with the novel beta crystalline form in order to increase the rate and efficiency of the melt crystallization. The melt crystallization is optionally carried out under reduced pressure of from 400 mm Hg to 0.1 mm Hg. The melt crystallization can also be carried out in an extruder or kneader as described in U.S. Pat. No. 4,683,326, the relevant parts of which are herein incorporated by reference.
An alternative process for the preparation of the beta crystalline modification of the compound of formula I is crystallizing or recrystallizing the compound of formula I from a mixture of an aromatic hydrocarbon solvent and an alcohol of 4 to 8 carbon atoms; from a mixture of an aliphatic ketone and an alcohol of 1 to 8 carbon atoms; or from a mixture of an aromatic hydrocarbon solvent and an aliphatic ketone.
Examples of aromatic hydrocarbon solvents useful in the instant process are benzene, toluene, o-xylene, m-xylene, p-xylene, 1,2,3-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, 1,2,4,5-tetramethylbenzene, ethylbenzene, cumene, o-cymene, m-cymene, p-cymene, o-diisopropylbenzene, m-diisopropylbenzene, p-diisopropylbenzene, and mixtures of such aromatic hydrocarbon solvents.
Examples of alcohols useful in the instant process are methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, tert-butyl alcohol, isobutanol, amyl alcohol, 1-hexanol, 2-ethylhexanol, 1-octanol and mixtures of such alkanols.
Examples of aliphatic ketones are acetone, 2-butanone, 2-pentanone, 3-pentanone, 2-heptanone and the like.
Differential scanning calorimetry (DSC) measurements are obtained on a TA Instrument Inc., 910 differential scanning calorimeter, with a 100 mL/min nitrogen purge, aligned aluminum pan, temperature scan at 5.degree. C./min to 230.degree. C.
X-ray diffraction patterns are recorded on a Philips Norelco X-ray Diffractometer unit, using Cu-K.alpha. radiation with a nickel filter.